Torque converter having integrated flex plate for hybrid electric vehicle

ABSTRACT

An assembly includes a torque converter concentric with an axis, a rotor hub drivably connected for rotation about the axis to an electric machine and selectively to an engine through a disconnect clutch, a coupler located between the rotor hub and torque converter, providing a rotational connection and an axial connection between the coupler and the rotor hub, and a flex plate providing second rotational and axial connections between the coupler and the torque converter.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a powertrain for hybrid electric vehicles,particularly to a powertrain module that is located between and securedto an engine output and a transmission input.

2. Description of the Prior Art

Hybrid electric vehicles (HEVs) have both an internal combustion engineand an electric machine, which are alternately, or in combination, usedto propel the vehicle. A variety of different powertrains are used inhybrid vehicles such as a parallel configuration, in which the engine isconnected to the motor by a disconnect clutch with the motor driving atorque converter input of an automatic power transmission. Thetransmission has an output which is connected to a differential coupledto the two driven wheels of the vehicle.

A need exists in the industry for a hybrid electric powertrain thatincludes a modular subassembly for use with a variety of engines andtransmissions, such that the module can be installed between and securedto an output of one of a number of engines and to an input of one of anumber of transmissions. The assembled powertrain may then be employedin a variety of vehicles. The module should include a hydraulicallyactuated disconnect clutch, the electric machine and suitable powerpaths between the engine and electric machine to the transmission input.Preferably, the module provides for hydraulic communication from thetransmission's hydraulic system to the clutch, a balance dam and theelectric machine. The module must provide an oil sump containinghydraulic fluid delivered to the module, and a path for continuallyreturning that fluid to the transmission's oil sump so that thetransmission pump is continually supplied reliably with fluid.

This module is sometimes called a front module (FM), since it is part ofthe modular hybrid transmission (MHT) and is bolted in front of thetransmission. Since this module adds length to the powertrain, themodule should be as short as possible. The attachment between the flexplate on the FM and the torque converter does not provide access, whichtorque converters normally have to engine flex plates resulting in addedlength to the powertrain.

SUMMARY OF THE INVENTION

An assembly includes a torque converter concentric with an axis, a rotorhub drivably connected for rotation about the axis to an electricmachine and selectively to an engine through a disconnect clutch, acoupler located between the rotor hub and torque converter, providing arotational connection and an axial connection between the coupler andthe rotor hub, and a flex plate providing second rotational and axialconnections between the coupler and the torque converter.

The assembly is axially short and allows easy installation of the frontmodule to transmission, providing an attachment method withoutincreasing the axial dimension of the powertrain.

The flex plate is integrated with the front of the torque converter. Theassembly does not require the conventional flex plate attachment boltsor nuts, but allows the torque converter to elastically expand andcontract without risk of damage to the transmission pump.

The scope of applicability of the preferred embodiment will becomeapparent from the following detailed description, claims and drawings.It should be understood, that the description and specific examples,although indicating preferred embodiments of the invention, are given byway of illustration only. Various changes and modifications to thedescribed embodiments and examples will become apparent to those skilledin the art.

DESCRIPTION OF THE DRAWINGS

The invention will be more readily understood by reference to thefollowing description, taken with the accompanying drawings, in which:

FIGS. 1A and 1B comprise a side cross-sectional view of a powertrainmodule showing a front connection to an engine output and a rearconnection to a transmission torque converter input.

FIG. 2 is side cross-sectional view of the powertrain of FIG. 1 showinga torque converter having a bolted, integrated flex plate; and

FIG. 3 is side cross-sectional view of the powertrain of FIG. 1 showinga torque converter having an elastically coupled integrated flex plate.

DESCRIPTION OF THE PREFERRED EMBODIMENT

FIGS. 1A and 1B illustrate a module 10 of a powertrain for a hybridelectric vehicle that includes an engine having a rotary output 12; atorsional damper 14, secured to the engine output 12; an input shaft 16,secured by a spline 18 to an output 20 of damper 14; a disconnect clutch22, supported on a clutch hub 24 that is secured by a spline 26 to inputshaft 16; an electric machine 28, which includes a stator 30 bolted to afront bulkhead 32 and a rotor 34 supported by a first leg 36 and asecond leg 38 for rotation about an axis 39; a rotor hub 40, securedpreferably by a weld to leg 38; and a flexplate 42, secured at one endby a spline connection 44 or by bolts 110 to rotor hub 40 and secured atthe opposite end by bolts 46 to a torque converter casing 48, whichencloses a hydrokinetic torque converter 49. The electric machine 28 maybe an electric motor or an electric motor-generator.

Torque converters suitable for use in the powertrain are disclosed inand described with reference to FIGS. 4a, 4b, 5, 12 and 15 of U.S.patent application Ser. No. 13/325,101, filed Dec. 14, 2011, the entiredisclosure of which is herein incorporated by reference.

The torque converter 49 includes a bladed impeller wheel located withinand secured to casing 48; a bladed turbine, driven hydrokinetically bythe impeller and secured by a spline 50 to the input shaft 52 of anautomatic transmission 54; and a bladed stator wheel, located betweenthe turbine and stator and secured to a stator shaft 56, which is heldagainst rotation on a transmission housing 58.

A rear bulkhead 60, secured by bolts 62 to the transmission housing 58,is fitted at its radial inner surface with a hydraulic seal 64, whichcontacts the radial outer surface of rotor hub 40.

A flywheel 66, secured by bolts 68 to the engine's rotary output 12,carries an engine starting gear 70, which is secured by a disc 72,welded to the starting gear and flywheel.

A bearing 74 supports the first leg 36 for rotation on the frontbulkhead 32. A bearing 76 supports the second leg 38 for rotation on therotor hub 40. A tube 78, aligned with axis 39 and supporting the rotor34 for rotation about the axis, is secured to the first leg 36 andsecond leg 38. Lips 80, 82 at the front and rear ends, respectively, oftube 78 may be rolled radially outward to secure the rotor 34 to tube 78and to prevent axial displacement of the rotor 34 relative to the tube.The inner surface of tube 78 is formed with an axial spline 81, which isengaged by the legs 36, 38 and alternate plates 83 of the disconnectclutch 22. The friction plates 84 of clutch 22 are secured by an axialspline formed on the radial outer surface of clutch hub 24.

A hydraulic servo for actuating clutch 22 includes a piston 86, balancedam 88, return spring 90 and hydraulic lines for transmitting actuatingpressure to the pressure control volume 92 at the right hand side ofpiston 86 and to the pressure balance volume 94 at the left hand side ofthe piston. Piston 86 moves leftward in a cylinder formed by the rearleg 38 when actuating pressure and hydraulic fluid is supplied to volume92, by the use of seals 151 and 152, thereby causing clutch 22 to engageand driveably connect rotor 34 and the engine output 12 through damper14, input shaft 16, clutch hub 24 and clutch 22.

Because the piston 86, balance dam 88 and return spring 90 are supportedon the rotor hub 40, rotational inertia of the piston 86, balance dam 88and return spring 90 is located on the output side, i.e., the rotor sideof clutch 22.

Rotor 34 is continually driveably connected to the transmission inputshaft 52 through the torque path that includes rear leg 38, rotor hub40, flexplate 42, torque converter casing 48, the hydrodynamic driveconnection between the torque converter impeller and turbine, which isconnected by spline 50 to transmission input shaft 52.

A resolver 100, a highly accurate type of rotary electrical transformerused for measuring degrees of rotation, is secured by bolts 102 to thefront bulkhead 32, is supported on the front bulkhead 32 and first leg,and is located axially between the front bulkhead 32 and rear bulkhead60.

The teeth of spline 44, which produces a rotary drive connection betweenflexplate 42 and rotor hub 40, are fitted together such that no lash isproduced when torque is transmitted between the flexplate and rotor hub.Flexplate 42 is formed with a thick walled portion 104 having a threadedhole 106 that terminate at a web 108. The external spline teeth onflexplate 42 are forced axially into engagement with the internal splineteeth on rotor hub 40 by bolts 110, which engage threaded holes in theright-hand end of rotor hub 40. The engaged spline teeth at the splineconnection 44 are disengaged upon removing bolts 110 and threading alarger bolt into hole 106 such that the bolt contacts web, therebyforcing flexplate axial rightward.

Rotor hub 40 is formed with multiple axially-directed hydraulic passages120 and laterally-directed passages 122, 124, 126, 128, 129, which carryhydraulic fluid and pressure to module 10 from the hydraulic system ofthe transmission 54. Passages 122, 124, 126, 128, 129 carry hydraulicfluid and pressure which includes to the control volume 92 of the servoof clutch 22 located at the right hand side of piston 86, to thepressure balance volume 94 between balance dam 88 and the piston, to avariable force solenoid (VFS) 130, and to the surfaces of rotor 34 andstator 30, which surfaces are cooled by the fluid. The rear bulkhead 60is formed with passage 128, which communicates hydraulically with VFS130.

The rear bulkhead 60 supports a sump 132, which contains fluid suppliedto module 10 from the hydraulic system of the transmission 54.Transmission 54 includes a sump 136, which contains hydraulic fluid thatis supplied by a transmission pump 134 to the transmission hydraulicsystem, from which fluid and control pressure is supplied to module 10,torque converter 49, transmission clutches and brakes, bearings, shafts,gears, etc.

A bearing 140, fitted in the front bulkhead 32, and a bearing 142,fitted in the rotor hub 40, support input shaft 16 in rotation aboutaxis 39. The front bulkhead 32 also supports the stator 30 in its properaxial and radial positions relative to the rotor 34. Bearing 76, fittedbetween rear bulkhead 60 and rotor hub 40, and bearing 142 support rotorhub 40 in rotation about axis 39. The front and rear bulkheads 32, 60together support rotor 34 in rotation about axis 39 due to bearing 74,fitted in bulkhead 32, and bearing 76, fitted in bulkhead 60.

Seal 64, fitted in the rear bulkhead 60, and seal 141, fitted in thefront bulkhead 32, prevent passage of fluid from module 10 locatedbetween the bulkheads 32, 60. Another dynamic seal 144 prevents passageof contaminants between the engine crankshaft 146 and module 10.

The components of module 10 are installed and assembled in the module.The assembled module can then be installed between and connected to theengine output 12 and the torque converter casing 48.

In operation, when the engine output 12 is driven by an engine, torqueis transmitted from the engine through rotor hub 40 and flexplate 42 tothe torque converter casing 48, provided that clutch 22 is engaged. Therotor 34 electric machine 28 is continually driveably connected throughtube 78, leg 38, rotor hub 40 and flexplate 42 to the torque convertercasing 48. Therefore, the torque converter casing 48 can be driven bythe engine alone, provided the electric machine 28 is off and clutch 22is engaged; by the electric machine alone, provided the engine is off orthe engine is operating and the clutch is disengaged; and by both theengine and electric machine concurrently.

In FIG. 2, input shaft 160 is driveably connected to the engine output12 through flywheel 66, flexplate 162 and spline 18. A bolt 164,installed through the front side of the front module, is insertedthrough a bore in input shaft 160 and through a web 108 of rotor hub 40.Bolt 164 is threaded into a tapped bore formed at the front side of acoupler shaft 166, thereby providing axial force continuity betweenrotor hub 40 and coupler shaft 166. Coupler shaft 166 is connected forrotation with rotor hub 40 through a spline connection 167, whichincludes mutually engaged axial spline teeth formed on an inner radialsurface of rotor hub 40 and axial spline teeth formed on the externalradial surface of coupler shaft 166.

A flex plate 168 is secured, preferably by a weld 170, to the torqueconverter casing 48 and by a series of rivets 172 to a flange 174 ofcoupler shaft 166, thereby securing rotor hub 40 to torque convertercasing 48. Bolt 164 secures torque converter 49 to the front module 10and carries axial load between the torque converter 49 and module 10.

In FIG. 3, input shaft 180 is driveably connected to the engine output12 through flywheel 66, flexplate 162 and spline 18. A flex plate 168 issecured, preferably by a weld 170, to the torque converter casing 48 andby a series of rivets 172 to a flange 174 of coupler shaft 182, therebysecuring rotor hub 40 to torque converter casing 48.

Coupler shaft 182 is connected for rotation to rotor hub 40 through aspline connection 184, which includes mutually engaged axial splineteeth formed on an inner radial surface of rotor hub 40 and axial splineteeth formed on the external radial surface of coupler shaft 182.

Rotor hub 40 is formed with an annular recess located at a radial innersurface of a bore in the rotor hub. Similarly, coupler shaft 182 isformed with an annular recess located at a radial outer surface andaligned axially with a recess of rotor hub 40. A C-clip 186 mutuallyengages the recess of rotor hub 40 and coupler shaft 182, therebysecuring torque converter 49 to the front module 10 and carrying axialload between the torque converter 49 and module 10.

The alternate assembly techniques of FIGS. 2 and 3 provide an attachmenttechnique that does not increase the length of the powertrain. Theoption of FIG. 3 allows service of the transmission and torque converterwithout removal of module 10 from the vehicle . . . .

In accordance with the provisions of the patent statutes, the preferredembodiment has been described. However, it should be noted that thealternate embodiments can be practiced otherwise than as specificallyillustrated and described.

The invention claimed is:
 1. An assembly, comprising: a torque converterconcentric with an axis; a rotor hub drivably connected for rotationabout the axis to an electric machine and selectively to an enginethrough a disconnect clutch; a coupler located between the rotor hub andtorque converter, providing a rotational connection and an axialconnection between the coupler and the rotor hub; a flex plate providingsecond rotational and axial connections between the coupler and thetorque converter; and wherein the axial connection includes a firstrecess located at a radial inner surface of a bore in the rotor hub, asecond recess located at a radial outer surface of the coupler andaligned axially with the first recess, and a connector mutually engagedwith the first and second recesses for transmitting axial force betweenthe rotor hub and the coupler.
 2. The assembly of claim 1, wherein therotational connection includes mutually engaged axial spline teethformed on an inner radial surface of the rotor hub and axial splineteeth formed on an external radial surface of the coupler.
 3. Theassembly of claim 1, wherein the connector is a c-clip located in thefirst and second recesses and elastically, releasably connecting therotor hub and the coupler.
 4. The assembly of claim 1, wherein the flexplate includes: a disc extending radially and axially from a radialinner connection between the disc and the coupler to a radial outerconnection between the disc and a casing of the torque converter.
 5. Theassembly of claim 4, wherein the radial inner connection comprises aseries of second connectors, and the radial outer connection is a weld.6. The assembly of claim 4, wherein the radial inner connectioncomprises a series of rivets.
 7. An assembly, comprising: a clutchalternately opening and closing a drive connection between an engine anda rotor of an electric machine; a rotor hub rotatably connected to therotor for rotation about an axis; a torque converter; a couplerproviding a rotational connection and an axial connection between thecoupler and the rotor hub; a flex plate providing second rotational andaxial connections between the coupler and the torque converter; andwherein the axial connection includes a first recess located at a radialinner surface of a bore in the rotor hub, a second recess located at aradial outer surface of the coupler and aligned axially with the firstrecess, and a connector mutually engaged with the first and secondrecesses for transmitting axial force between the rotor hub and thecoupler.
 8. The assembly of claim 7, wherein the rotational connectionincludes mutually engaged axial spline teeth formed on an inner radialsurface of the rotor hub and axial spline teeth formed on an externalradial surface of the coupler.
 9. The assembly of claim 7, wherein theconnector is a c-clip located in the first and second recesses andelastically, releasably connecting the rotor hub and the coupler. 10.The assembly of claim 7, wherein the flex plate includes: a discextending radially and axially from a radial inner connection betweenthe disc and the coupler to a radial outer connection between the discand a casing of the torque converter.
 11. The assembly of claim 10,wherein the radial inner connection comprises a series of secondconnectors, and the radial outer connection is a weld.
 12. The assemblyof claim 10, wherein the radial inner connection comprises a series ofrivets.
 13. An assembly, comprising: a torque converter; a rotor hubdriveably connected to a motor and selectively connected to an engine; acoupler providing rotational and axial connections between the rotor huband torque converter, the axial connection including a recess in a rotorhub bore, a second recess in a coupler outer surface, and a connectorengaging the recesses to transmit axial force; a flex plate connectingthe coupler to the torque converter.
 14. The assembly of claim 13,wherein the connector is a C-clip located in the recesses andelastically, releasably connecting the rotor hub and the coupler.